The primary goal of this program is to perfect methods for implementing atrial cardiac pacemakers with catheter electrodes. Most synchronous pacemakers use myocardial electrodes which require major surgery for their implantation. Catheter electrodes, which are now used for most nonsynchronous pacemakers, have had difficulties in the synchronous application. The use of a very flexible catheter electrode with magnet tip to aid in the placement of the tip is well suited to this application. Methods will be investigated for developing suitable flexible electrodes and for holding atrial catheter electrodes in place until normal fibrous tissue grows and provides long-term fixation. A secondary goal will be to use the same electrode for temporary fixation in the right ventricle.